TWI507760B - Displacement detecting device - Google Patents

Description

Displacement detecting device

The present invention contains the subject matter of the Japanese Patent Application No. 2010-140904, filed on Jun.

The present invention relates to a displacement detecting device that detects the amount of displacement (movement) of a diffraction grating (one scale) by using interference of light.

Conventionally, a displacement detecting device having a scale and a detecting head has been widely used as a measuring instrument for precisely measuring linear displacement, rotational displacement, and the like. In recent years, displacement detecting devices using light or laser light emitted from a light emitting diode have been employed. Further, there is a need for a high-resolution displacement detecting device capable of measuring a displacement of 1 nm or less.

One of the conventional displacement detecting devices is described in, for example, Japanese Unexamined Patent Application Publication No. No. 2009-257841. In the displacement detecting device described in Japanese Unexamined Patent Application Publication No. No. 2009-257841, light emitted from a light source is separated into two beams by a beam splitter, and two beams of light are respectively reflected by the two reflectors, and The two beams of reflected light are illuminated at the same location of a diffraction grating.

Further, the two beams of light irradiated to one diffraction grating are diffracted by the diffraction grating to generate two first-order diffracted lights. The first order diffracted light is each reflected by a reflector (such as a mirror) and is again incident on the diffraction grating along the same light path as the light path of the diffraction grating from the light source. In this way, the two second-order diffracted lights are generated by diffracting the diffraction grating twice.

Next, the second-order diffracted light is superposed on each other by a spectroscope to interfere with each other, and the interference light of the two second-order diffracted lights forms an image on a light-receiving element. Further, an interference signal is detected by the light-receiving element based on the interference light, and a difference in movement between the second-order diffracted lights is obtained based on the interference signal to detect the amount of movement of the diffraction grating.

Further, there is another displacement detecting device which is described in Japanese Unexamined Patent Application Publication No. No. 2007-218833, in which two beams of light obtained by separating a light emitted from a light source by a beam splitter are irradiated Diffraction of two different positions of the grating.

However, in the displacement detecting device described in Japanese Unexamined Patent Application Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. It is equal to the incident angle of light reflected by the reflector and re-incident on the diffraction grating. Therefore, in the second-order diffracted light that is diffracted twice by the diffraction grating, there is a concern that undesired stray light caused by multiple reflections of each component may coincide with the interference light. As a result, since the undesired stray light coincides with the interference light, noise is generated, thereby reducing the detection accuracy.

Some methods have been proposed, such as tilting the components, setting a phase plate and/or the like to avoid stray light from overlapping the interference light. However, if a phase plate and/or the like is provided, the number of components will increase.

Further, in the technique described in Japanese Unexamined Patent Application Publication No. No. 2007-218833, the two beams of light are irradiated at two different positions of the diffraction grating. Therefore, if the surface accuracy of the surface of the diffraction grating is low, a change in the optical path length of each beam of light is caused. As a result, changes in the length of the optical path are detected as errors.

Moreover, in the ultra-precision positioning platform having a tilt mechanism of the current semiconductor manufacturing equipment, inspection equipment, etc., it is necessary to have a high-speed response with a displacement detection accuracy of 1 nm or less while still maintaining an allowable tilt and clearance as a linear coding. Device. Therefore, even the above slight error must be eliminated.

An object of the present invention is to provide a displacement detecting device in which when the light emitted from the light source is diffracted twice by the diffraction grating, the incident angle and the output angle are different from each other, and thus the interference light and the multiple reflection of each component The stray light caused does not overlap each other, so the detection accuracy can be improved.

In order to solve the above problems and achieve the above object of the present invention, a displacement detecting device according to an aspect of the present invention includes: a substantially plate-shaped diffraction grating suitable for diffracting light; and a grating interferometer adapted to light Irradiating in a diffraction grating, wherein the illumination light is diffracted into two beams each having a positive order and a negative order, so that the two beams of the diffracted light interfere with each other and generate an interference signal; and a relative position information output portion is applicable The relative position information of the diffraction grating is detected according to the interference signal generated by the grating interferometer, and the grating interferometer comprises: a light source adapted to illuminate the light on the diffraction grating: two reflectors, suitable for the reflection to be wound Passing two first-order diffracted rays that are diffracted by the grating, and causing the reflected first-order diffracted light to be incident on the diffraction grating at substantially the same position as the light from the light source; a spectroscope Suitable for superimposing two second-order diffracted lights that are diffracted twice by the diffraction grating; and a receiver adapted to receive the second-order diffracted light that is superposed by the spectroscopes to generate an interference signal. The reflector causes the first-order diffracted light to be incident on the diffraction angle at an angle different from the incident angle of the light incident from the light source to the diffraction grating and the angle at which the first-order diffracted light is transmitted through the diffraction grating or reflected by the diffraction grating. On the grating.

According to the displacement detecting device of the present invention, the output angle of the first-order diffracted light diffracted by the diffraction grating and the incident angle of the first-order diffracted light incident on the diffraction grating by the reflector are set to each other by the reflector. different. Therefore, the light path of the second-order diffracted light that is diffracted twice is not parallel to the light path of the first-order diffracted light or the light path of the light irradiated from the light source on the diffraction grating. As a result, the possibility that the stray light due to the multiple reflection of the component coincides with the interference light can be eliminated, so that the interference intensity can be accurately detected.

Further, the first-order diffracted light reflected by the reflector is incident on the diffraction grating at a position substantially the same as the position at which the light from the light source is incident on the diffraction grating. As a result, the error caused by the surface roughness of the diffraction grating can be eliminated, and thus the detection accuracy can be improved.

A preferred embodiment of the displacement detecting device embodying the present invention will be described below with reference to Figs. In the drawings, like elements are denoted by the same reference numerals. It is also to be noted that the invention is not limited to such embodiments.

The instructions will be in the following order.

1. First Embodiment

1-1. Example of the structure of the displacement detecting device

1-2. Operation of the displacement detecting device

2. Second Embodiment

3. Third embodiment

4. Fourth Embodiment

5. Fifth embodiment

6. Sixth Embodiment

7. Variations of the diffraction grating

<1. First Embodiment>

First, the first embodiment (hereinafter referred to as "this embodiment") according to the present invention will be described below with reference to Figs. 1 to 3.

1-1. Example of the structure of the displacement detecting device

1 is a perspective view showing an optical system of one of the displacement detecting devices 1 according to the first embodiment of the present invention, and FIG. 2 is a side view showing an optical system of one of the displacement detecting devices 1.

The displacement detecting device 1 according to the present embodiment can use a reflective composite diffraction grating to detect a two-dimensional (ie, planar) displacement detecting device. As shown in FIGS. 1 and 2, the displacement detecting device 1 includes a first grating interferometer 4, a second grating interferometer 5, a first relative position information output unit 6, and a second relative position information output. The portion 7 (see FIG. 2), wherein the first grating interferometer 4 and the second grating interferometer 5 share a composite diffraction grating 2 and a light source 3.

Fig. 6 is a view showing the composite diffraction grating 2 as seen from the upper side.

As shown in Fig. 3, the composite diffraction grating 2 has a first diffraction grating 2a and a second diffraction grating 2b. Each of the first diffraction grating 2a and the second diffraction grating 2b is formed by forming narrow slits s at equal intervals.

The slit s of the first diffraction grating 2a is formed to be perpendicular to the first grating vector direction C parallel to the surface of the composite diffraction grating 2. The distance Λa between the first diffraction gratings 2a is set to d ₁ . Incidentally, the slit s of the composite diffraction grating 2 is only an example; the diffraction grating may be a reflective diffraction grating having a concave-convex shape, or a transmission volume hologram.

The slit s of the second diffraction grating 2b is formed to be perpendicular to the second grating vector direction D which is parallel to the surface of the composite diffraction grating 2 and which is inclined by an angle θa with respect to the first grating vector direction C. The distance Λb between the second diffraction gratings 2b is set to d ₂ . Incidentally, the distance Λb between the first diffraction grating 2a and the second diffraction grating 2b may be equal to or different from each other. Also, the angle θa may be equal to or different from 90 degrees.

4 is a diagram for explaining the relationship between the first grating vector direction C and the second grating vector direction D of the composite diffraction grating 2, and a virtual surface of the first grating interferometer 4 and the second grating interferometer 5 A diagram of the relationship between a virtual surface.

Here, as shown in Fig. 4, any position at which the light of the composite diffraction grating 2 is incident is defined as an irradiation point P. Further, a plane passing through the irradiation point P and parallel to the first grating vector direction C and perpendicular to the surface of the composite diffraction grating 2 is defined as a first virtual surface 10A. Further, a plane passing through the irradiation point P and parallel to the second grating vector direction D and perpendicular to the surface of the composite diffraction grating 2 is defined as a second virtual surface 10B. Incidentally, the direction perpendicular to the composite diffraction grating 2 is defined as a third direction Z.

The first grating interferometer 4 is disposed to correspond to the first virtual surface 10A, and the second grating interferometer 5 is disposed to correspond to the second virtual surface 10B. The first grating interferometer 4 generates an interference signal of light diffracted by the first diffraction grating 2a, and the second grating interferometer 5 generates an interference signal of light diffracted by the second diffraction grating 2b.

Incidentally, in the present embodiment, the first grating vector direction C of the composite diffraction grating 2 is aligned with a first measurement direction, and the second grating vector direction D of the composite diffraction grating 2 is a second Measure direction alignment.

As shown in FIG. 2, since the first grating interferometer 4 and the second grating interferometer 5 have the same structure, the description will focus on the first grating interferometer 4. Further, among the elements of the second grating interferometer 5, the same elements as those of the first grating interferometer 4 are denoted by the symbols formed by adding "B" to the element symbols of the first grating interferometer 4.

The first grating interferometer 4 includes the light source 3, the lens 11, the first reflector 12, the second reflector 13, the first mirror 14, the second mirror 16, the spectroscope 17, the first light receiving portion 18, and the second light receiving unit. Part 19.

The light source 3 is arranged substantially perpendicular to the surface of the composite diffraction grating 2. Incidentally, the light source 3 also serves as a light source of the second grating interferometer 5. A coherent light source is preferably used as the light source 3. Examples of coherent light sources include gas lasers, semiconductor laser diodes, ultra-cold light diodes, luminescent diodes, and the like.

Incidentally, the present embodiment is described using an example in which the light source 3 is disposed in the first grating interferometer 4; however, the present invention is not limited to this configuration. For example, the present invention also includes a configuration in which a light system is supplied from a light source disposed on the outer side of the first grating interferometer 4 via an optical fiber. Further, by attaching the light source to the optical fiber in a detachable manner, the maintenance of the light source can be performed at a place separated from the displacement detecting device 1, so that workability can be improved.

Further, the lens 11 is mounted between the light source 3 and the composite diffraction grating 2. The lens 11 condenses the light L emitted from the light source 3 into any diameter. The lens 11 can be subjected to achromatic processing depending on the wavelength range used. By performing the achromatic processing on the lens 11, the influence of the change in the focal length due to the wavelength change of the light source 3 can be reduced. As a result, the displacement can be measured more stably.

Incidentally, the light source 3 and the lens 11 are elements common to the second grating interferometer.

The first reflector 12 and the second reflector 13 are arranged along the first grating vector direction C and the light source 3 is interposed therebetween. Incidentally, in the second grating interferometer 5, the first reflector 12B and the second reflector 13B are arranged along the second grating vector direction D. Each of the first reflector 12 and the second reflector 13 is a prism body, and is suitable for re-reflecting the light L reflected from the composite diffraction grating 2 to the composite diffraction grating 2. Incidentally, each of the first reflector 12 and the second reflector 13 is formed by combining a plurality of mirrors in place of the prism body.

The first mirror 14 and the second mirror 16 are arranged along the first grating vector direction C and the light source 3 is interposed therebetween. Incidentally, in the second grating interferometer 5, the first mirror 14B and the second mirror 16B are arranged along the second grating vector direction D. Each of the first mirror 14 and the second mirror 16 is adapted to reflect the light L that is twice diffracted by the composite diffraction grating 2 toward the spectroscope 17.

Further, the spectroscope 17 is mounted above the light source 3 in the third direction Z. The spectroscope 17 is adapted to cause the two beams of the light L reflected from the first mirror 14 and the second mirror 16 to overlap each other, thereby causing the two beams of the light L to interfere with each other and to separate the light into two beams. Further, the first light receiving unit 18 and the second light receiving unit 19 are disposed at the light exit opening of the spectroscope 17. Further, the first light receiving unit 18 and the second light receiving unit 19 are connected to the first relative position information output unit 6.

Further, the first light receiving unit 18B and the second light receiving unit 19B of the second grating interferometer 5 are connected to the second relative position information output unit 7.

Incidentally, the light reflecting surfaces of the first reflector 12, the second reflector 13, the first mirror 14, and the second mirror 16 may be made of a metal thin film such as a gold film. Therefore, the change in the wavelength and the polarization property caused by the humidity change can be suppressed as compared with the general reflective surface made of the dielectric multilayer body, so that the position detection can be stably performed.

Further, the first grating interferometer 4, the second grating interferometer 5, the first relative position information output unit 6, and the second relative position information output unit 7 constitute a non-contact sensor.

1-2. Operation of the displacement detecting device

Next, the operation of the displacement detecting device 1 will be described below with reference to Figures 1, 2, 5 and 6. Fig. 5 is a view showing an enlarged main portion of one of the displacement detecting devices 1.

As shown in Fig. 1, the light L emitted from the light source passes through the lens 11 and is incident on the surface of the composite diffraction grating 2 substantially perpendicularly at any irradiation point P. Further, the light L is diffracted by the first diffraction grating 2a and the second diffraction grating 2b of the hybrid diffraction grating 2 into four first-order windings along the first grating vector direction C and the second grating vector direction D. Shoot light.

Specifically, as shown in FIG. 5, the irradiation light L is incident at the point P, since it is a composite diffraction grating of the first diffraction grating and diffracted 2a made of the positive and negative first order diffracted light L _1, -L ₁ . More specifically, the first-order diffracted light L ₁ in the positive direction (ie, the moving direction) of the first grating vector direction C of the composite diffraction grating 2 is positive, and the first in the negative direction of the first grating vector direction C The first-order diffracted light L ₁ is negative. The same applies to the second diffraction grating 2b, and thus the description is omitted here.

Here, the diffraction angle of the diffracted light can be obtained by the following general formula (1).

Sinθ _in +sinθ _out =n‧λ/Λ (1)

Incidentally, the angle "θ _in " represents the incident angle of light incident on the composite diffraction grating 2, and the angle "θ _out " is a diffraction angle of light diffracted from the composite diffraction grating 2 (in this embodiment) Medium is the angle of reflection). Further, "Λ" indicates the pitch (width) of the grating, "λ" indicates the wavelength of the light L, and "n" indicates the number of times of diffraction. In the present invention, since the light is incident substantially perpendicularly on the composite diffraction grating 2, the angle θ _in is zero.

The first-order diffracted light L ₁ , -L ₁ is reflected by the composite diffraction grating 2 toward the first reflector 12 and the second reflector 13 of the first grating interferometer 4 at a first output angle θ ₁ (diffraction ). The positive first-order diffracted light L ₁ moves toward the first reflector 12 , and the negative first-order diffracted light −L ₁ moves toward the second reflector 13 . Further, the two first-order diffracted lights L ₁ and -L ₁ are reflected by the first reflector 12 and the second reflector 13 and are again incident on the irradiation spot P of the composite diffraction grating 2. Therefore, the two first-order diffracted lights L ₁ , -L _{1 are} again diffracted by the composite diffraction grating 2 to become the second-order diffracted light L ₂ , -L ₂ and are emitted from the composite diffraction grating 2.

At this time, the two first-order diffracted lights L ₁ , -L ₁ are reflected twice in the first reflector 12 or the second reflector 13. Thus, it is reflected by the first reflector 13 and second reflector 12 and again enters the diffraction grating 2 of the compound of formula two first-order diffracted light L _1, -L ₁ incident angle of θ _2, and the output angle θ based ₁ different. Incidentally, the number of times of reflection of the first-order diffracted lights L ₁ and -L ₁ reflected by the first reflector 12 and the second reflector 13 is not limited to two. For example, the two first-order diffracted lights L ₁ , -L ₁ are reflected three times or more in the first reflector 12 and the second reflector 13.

Fig. 6 is a view showing another example of the main portion of the displacement detecting device 1 as seen from the upper side of the irradiation spot P.

Incidentally, Fig. 5 shows an example in which the first-order diffracted light L ₁ , -L ₁ and the second-order diffracted light L ₂ , -L ₂ are disposed on the virtual surfaces 10A, 10B. However, as shown in Fig. 6, the first-order diffracted light L ₁ , -L ₁ and the second-order diffracted light L ₂ , -L ₂ do not need to be disposed in the virtual surfaces 10A, 10B. Since the first-order diffracted light L ₁ , -L ₁ is incident on the diffraction grating at an incident angle θ ₂ , if the first-order diffracted light L ₁ , -L _{1 is} disposed on the virtual surface 10A, 10B, there is The zero-order light of the first-order diffracted light L ₁ (ie, the light L) coincides with the possibility of the first-order diffracted light -L ₁ . Similarly, there will be the first order diffracted light of the zero order light -L ₁ (i.e., the light L) coincides with the first order diffracted light of the possibility of L _1.

In order to avoid this problem, as shown in Fig. 6, the first-order diffracted lights L ₁ , -L ₁ can also be incident at an angle θ ₄ as viewed from the upper side of the composite diffraction grating 2. With this configuration, it is possible to effectively prevent the zero-order light of the first-order diffracted light L ₁ (ie, the light L) from overlapping the first-order diffracted light -L ₁ and the first-order diffracted light - L ₁ of the zero-order light. (i.e., the light L) overlap. problems first order diffracted light of L _1, and thereby preventing undesirable stray light back to the light source 3.

Further, the composite diffraction grating 2 is twice the second diffraction order diffracted light L _2, -L ₂ to the second output angle θ ₃ is emitted (i.e. diffraction), this second output different from the first angle θ ₃ 1 output angle θ ₁ and incident angle θ ₂ . Therefore, the second-order diffracted light L ₂ , -L ₂ does not become parallel to the first-order diffracted light L ₁ , -L ₁ or the incident light L. Thus, the possibility that stray light caused by multiple reflections of the components coincides with the interference light can be eliminated.

Further, when the second diffraction is performed, the light is also irradiated to the same irradiation point P as the first diffraction. Therefore, there is no fear of the influence of the surface precision of the surface of the composite diffraction grating 2. Therefore, the error due to the surface roughness of the composite diffraction grating 2 can be eliminated.

Next, the second-order diffracted lights L ₂ and -L ₂ are incident on the first mirror 14 and the second mirror 16, respectively. Specifically, the second-order diffracted light L _{2 is} incident on the first mirror 14 and is reflected by the first mirror 14 toward the spectroscope 17. Further, the second-order diffracted light -L _{2 is} incident on the second mirror 16 and is reflected by the second mirror 16 toward the spectroscope 17.

Further, the two second-order diffracted lights L ₂ , -L ₂ are superposed on each other to interfere with each other to become the interference light L _d . Further, the interference light L _d is split into two light beams by the spectroscope 17, and the two light beams are guided to the first light receiving unit 18 and the second light receiving unit 19, respectively.

In the first light receiving section 18, the interference light L _d is received, and the received interference light L _d is photoelectrically converted to "Acos (4Kx + δ)" represents the interference signal. In this representation, "A" represents the amplitude of the interference signal, and "K" represents the wave number represented by "2Π/Λ", and "x" represents the movement of the composite diffraction grating 2 in the direction of the first grating vector C. Quantity, and "δ" represents the initial phase.

Here, as shown in Fig. 5, when initially incident on the composite diffraction grating 2, the light L is separated into positive and negative two first-order diffracted lights L ₁ , -L ₁ . Further, the first-order diffracted light L ₁ is reflected by the second reflector 13 and is diffracted twice (2K) by the hybrid diffraction grating 2. Similarly, the first-order diffracted light -L ₁ is diffracted twice (2K) by the composite diffraction grating 2. Further, by being overlapped by the spectroscope 17, the coefficient of "x" becomes 2K + 2K = 4K. Therefore, as the above representation of the interference signal, "x" is multiplied by "4K".

Therefore, when the composite diffraction grating 2 moves toward the first grating vector direction C, the four wavelengths of each pitch (ie, 1 Λ) of the first diffraction grating 2a (ie, 4 bright and dark lights) The ring pattern can be obtained by the first light receiving portion 18. Therefore, the displacement can be detected with high resolution.

Incidentally, the phase of the signal acquired by the second light receiving unit 19 is different from the phase of the interference signal acquired by the first light receiving unit 18 by 90 degrees. Therefore, a sinusoidal signal and a cosine signal can be obtained. Further, the amount of displacement in the first raster vector direction C can be detected by outputting the sinusoidal signal and the cosine signal to the first relative position information output unit 6. The details of the first relative position information output portion 6 are subsequently explained in other embodiments.

In the positive and negative first-order diffracted lights L ₁ , -L ₁ which are diffracted by the composite diffraction grating 2, not only the positive first-order diffracted light L ₁ but also the negative first-order diffracted light - L ₁ are used. To generate an interference signal. Since the negative first-order diffracted light -L ₁ or the positive first-order diffracted light L ₁ does not become undesired stray light, the interference intensity can be accurately detected. Further, the amount of light can be improved by 19 L _d of the first light receiving portion 18 and the second interference light receiving portion, and the detection accuracy can be improved.

Incidentally, the displacement amount in the second grating vector direction D of the second grating interferometer 5 is two diffracted lights L ₁ that have been incident on the irradiation point P from the light source 3 and are diffracted along the second grating vector direction D, - L ₁ detection. Since the other aspect of the operation of detecting the displacement amount in the second raster vector direction D is the same as the operation of detecting the displacement amount in the first raster vector direction C, the description thereof will be omitted.

In the above manner, the light L emitted from one light source 3 can be effectively used by the first grating interferometer 4 and the second grating interferometer 5. Therefore, the displacement amount of the composite diffraction grating 2 in the first grating vector direction C and the second grating vector direction D can be detected by the light L emitted from one light source 3. Therefore, it is not necessary to separately prepare two light sources for the interferometers 4, 5 and thus the number of components can be reduced.

<2. Second Embodiment>

Next, a displacement detecting device 31 according to a second embodiment of the present invention will be described with reference to Figs.

Fig. 7 is a side view showing the optical system of the displacement detecting device 31 according to the second embodiment, and Fig. 8 is a block diagram showing the relative position information output portion of the displacement detecting device 31.

The displacement detecting device 31 according to the second embodiment is different from the displacement detecting device 1 of the first embodiment in that a lens is disposed between the composite diffraction grating 2 and each of the reflectors and the first light receiving portion and Since the structure of the second light receiving unit is different, the following description will focus on such differences. Therefore, in the displacement detecting device 31 of the second embodiment, the similar elements are denoted by the same reference numerals as those of the displacement detecting device 1 of the first embodiment, and the description thereof will be omitted.

As shown in FIG. 7, the displacement detecting device 31 includes a composite diffraction grating 2, a light source 3, a first grating interferometer 34, a second grating interferometer 35, a first relative position information output unit 6, and a second Relative position information output unit 7. The light source 3 of the displacement detecting device 31 according to the second embodiment is suitable for emitting circularly polarized light.

Since the first grating interferometer 34 and the second grating interferometer 35 have the same structure, the description herein will focus on the first grating interferometer 34. Further, among the elements of the second grating interferometer 35, the same components as those of the first grating interferometer 34 are indicated by a symbol formed by adding "B" to the element symbol of the first grating interferometer 34.

As shown in Fig. 7, a first lens 37 is mounted between the composite diffraction grating 2 and the first reflector 12. Further, a second lens 38 is mounted between the composite diffraction grating 2 and the second reflector 13.

The focal length of the first lens 37 is equal to the distance between the composite diffraction grating 2 and the lens 11. The focal length of the second lens 38 is also equal to the distance between the composite diffraction grating 2 and the lens 11.

Therefore, since the focal lengths of both the first lens 37 and the second lens 38 are equal to the distance between the composite diffraction grating 2 and the lens 11, after the composite diffraction grating 2 is inclined, it passes through the first lens 37. The light path is substantially parallel to the light path after passing through the first lens 37 when the composite diffraction grating 2 is not inclined. Further, since the first reflector 12 and the second reflector 13 are each formed of two mirrors, when incident on the composite diffraction grating 2 again, the light can be irradiated close to the irradiation point P. With this configuration, the measurement error caused by the tilt of the composite diffraction grating 2 can be reduced.

As a result, the second incident point formed by the light reflected by the first reflector 12 and the second reflector 13 and incident on the composite diffraction grating 2 is unlikely to deviate from the arbitrary irradiation point P. Also, the tolerance of the tilt of the composite diffraction grating 2 can be improved.

A first phase plate 39 and a second phase plate 40 are disposed on the side of the light incident port of the spectroscope 17. Specifically, the first phase plate 39 is disposed on the optical path between the spectroscope 17 and the first mirror 14 , and the second phase plate 40 is disposed on the optical path between the spectroscope 17 and the second mirror 16 .

Each of the first phase plate 39 and the second phase plate 40 includes a one-fourth wave plate, and is, for example, adapted to convert the second-order diffracted light L ₂ , -L ₂ (which is circularly polarized light) into linearly polarized light. Further, in order to convert the transmitted second-order diffracted lights L ₂ and -L ₂ into linearly polarized lights perpendicular to each other, the first phase plate 39 and the second phase plate 40 are disposed such that their crystal axes are perpendicular to each other.

Further, the first light receiving unit 18 includes the first polarization beam splitter 42 , the first light receiving element 43 , and the second light receiving element 44 . The second light receiving unit 19 includes a second polarization beam splitter 46 , a third light receiving element 47 , and a fourth light receiving element 48 .

The third lens 49 is disposed in the optical path between the spectroscope 17 and the first light receiving unit 18, and the third phase plate 41 and the fourth lens 50 are disposed between the spectroscope 17 and the second light receiving unit 19. On the light path.

The second-order diffracted light L ₂ , -L ₂ , which has been converted by the first phase plate 39 and the second phase plate 40 into two mutually perpendicular linearly polarized lights, are superposed on each other and separated into two beams by the beam splitter 17, and two The separated beams are guided to the third lens 49 and the fourth lens 50, respectively.

Here, the first polarization beam splitter 42 is obliquely mounted such that the polarization directions of the two second-order diffracted lights L ₂ , -L ₂ are inclined at an angle of 45 degrees with respect to the incident plane of the first polarization beam splitter 42, respectively. The polarization directions of the two second-order diffracted lights L ₂ , -L ₂ are different from each other by 90 degrees.

Here, the first polarization beam splitter 42 is adapted to separate the light by reflecting the interference light having the s-polarization component and transmitting the interference light having the p-polarization component.

With this arrangement, the two second-order diffracted lights L ₂ and -L ₂ respectively have a p-polarizing component and an s-polarizing component for the first polarizing beam splitter 42. Therefore, since the two second-order diffracted lights L ₂ and -L ₂ transmitted through the first polarization beam splitter 42 are p-polarized components having the same polarization direction, for example, two second-order diffracted lights L ₂ , -L ₂ can interfere with each other.

Similarly, the two second-order diffracted lights L ₂ and -L ₂ reflected by the first polarization beam splitter 42 are s-polarized for the first polarization beam splitter 42 and are reflected by the first polarization beam splitter 42. The two second-order diffracted lights L ₂ , -L ₂ have the same polarization direction, so that the two second-order diffracted lights L ₂ , -L ₂ can interfere with each other.

The interference light L _d transmitted through the first polarization beam splitter 42 is received by the first light receiving element 43. Further, the interference light L _d reflected by the first polarization beam splitter 42 is received by the second light receiving element 44. Here, the phase of the signal photoelectrically converted by the first light receiving element 43 and the phase of the signal photoelectrically converted by the second light receiving element 44 are different from each other by 180 degrees.

Similarly to the displacement detecting device 1 of the first embodiment, the interference signal represented by "Acos (4Kx + δ)" is obtained by the first light receiving element 43 and the second light receiving element 44.

On the other hand, the two second-order diffracted lights L ₂ and -L ₂ guided to the fourth lens 50 are incident on the third phase plate 41, and are formed of a one-fourth wave plate or the like. The two second-order diffracted lights L ₂ , -L ₂ (which are linearly polarized with a polarization direction that is different from each other by 90 degrees) are transmitted through the third phase plate 41 and thereby become two circularly polarized lights having opposite directions of rotation. Further, since the two circularly polarized lights having the opposite rotation directions are located in the same light path, they are coincident with each other to thereby become linearly polarized light; and this linearly polarized light is incident on the second polarization beam splitter 46.

The linearly polarized s-polarized component is reflected by the second polarizing beam splitter 46 and received by the third light receiving element 47. Further, the p-polarized component passes through the second polarization beam splitter 46 and is received by the fourth light receiving element 48.

The linear polarization incident on the second polarization beam splitter 46 is generated by superposing two circularly polarized lights having opposite rotation directions. Further, the polarization direction of the linearly polarized light incident on the second polarization beam splitter 46 is rotated once every time the composite diffraction grating 2 moves Λ/2 in the first grating vector direction C. Therefore, in the same manner, the interference signal represented by "Acos (4Kx + δ)" is obtained by the third light receiving element 47 and the fourth light receiving element 48. Here, "δ" represents the initial phase.

Further, the phase of the signal photoelectrically converted by the third light receiving element 47 and the phase of the signal photoelectrically converted by the fourth light receiving element 48 are different from each other by 180 degrees.

Incidentally, in the present embodiment, the second polarization beam splitter 46 for separating the light beams received by the third light receiving element 47 and the fourth light receiving element 48 is applied at an angle of 45 degrees with respect to the first polarization beam splitter 42. installation. Therefore, the phases of the signals obtained by the third light receiving element 47 and the fourth light receiving element 48 and the signals obtained by the first light receiving element 43 and the second light receiving element 44 are different from each other by 90 degrees.

Therefore, a signal obtained by the first light receiving element 43 and the second light receiving element 44 can be used as a sinusoidal signal, and a signal obtained by the third light receiving element 47 and the fourth light receiving element 48 can be used as a cosine signal to obtain a Lissajous Such as the signal (Lissajous signal).

The signal obtained by the light receiving element is calculated by the first relative position information output unit 6, and the displacement amount of the surface to be measured is calculated.

For example, as shown in FIG. 8, the first relative position information output unit 6 includes a first differential amplifier 51a, a second differential amplifier 51b, a first A/D converter 52a, a second A/D converter 52b, and waveform correction. The processing unit 53 and the incremental signal generator 54.

For example, in the first relative position information output unit 6 of the present embodiment, the signal obtained by the first light receiving element 43 and the signal obtained by the second light receiving element 44 are 180 degrees apart from each other by the first differential amplifier. 51a is differentially amplified to eliminate the DC component of the interference signal.

Further, this signal is A/D-converted by the first A/D converter 52a, and the amplitude, offset, and phase of the signal are corrected by the waveform correction processing unit 53. In an incremental signal generator 54, this signal is for example calculated as an A-phase increment signal.

Similarly, the signal obtained by the third light receiving element 47 and the signal obtained by the fourth light receiving element 48 are differentially amplified by the second differential amplifier 51b, and A/D converted by the second A/D converter 52b. Further, the amplitude, offset, and phase of the signal are corrected by the waveform correction processing unit 53 and the signal is output from the signal generator 54 as a B-phase increment signal whose phase is different from the A-phase increment signal by 90 degrees.

Regardless of whether the two phases of the incremental signal obtained in the above manner are positive or negative, it is discriminated by a pulse discriminating circuit or the like (not shown), and thereby, regardless of the displacement of the surface to be measured in the direction C of the first grating vector Whether the quantity is detected in the positive or negative direction can be detected.

Further, measurement can be performed by counting the number of pulses of the incremental signal by a counter (not shown) to observe how many of the periodic changes in the intensity of the interference light of the two-order diffracted light L ₂ and -L ₂ are. Therefore, the amount of displacement in the first grating vector direction C can be detected by the above processing.

Incidentally, the relative position information output by the first relative position information output unit 6 of the embodiment may be the two phases of the incremental signal or the displacement amount and direction calculated according to the two phases of the incremental signal. signal.

The second relative position information output unit 7 has the same structure as the first relative position information output unit 6, and the description thereof is omitted here.

Since the other configuration of the displacement detecting device 31 is the same as that of the displacement detecting device 1 of the first embodiment, the description thereof is omitted here. The same advantages as the displacement detecting device 1 of the first embodiment can be achieved by the displacement detecting device 31 having the above configuration.

<3. Third embodiment>

Next, a displacement detecting device 61 according to a third embodiment of the present invention will be described with reference to Figs. 9, 10A and 10B.

Figure 9 is a side view showing the optical system of the displacement detecting device 61 according to the third embodiment of the present invention; each of Figs. 10A and 10B shows one of the displacement detecting devices 31 of the third embodiment of the present invention. A magnified view of the main part.

The displacement detecting device 61 of the third embodiment differs from the displacement detecting device 31 of the second embodiment in the structure of the first lens and the second lens. Therefore, in the displacement detecting device 61 of the third embodiment, similar elements are denoted by the same reference numerals as those of the displacement detecting device 31 of the second embodiment, and the explanation thereof is omitted, so that the following description will focus on the first lens and The second lens.

As shown in FIG. 9, the displacement detecting device 61 includes a first grating interferometer 64 and a second grating interferometer 65. The first lens group 62 is disposed in the optical path between the first reflector 12 and the composite diffraction grating 2 of the first grating interferometer 64. Further, a second lens group 63 is disposed in the optical path between the second reflector 13 and the composite diffraction grating 2.

The first lens group 62 includes a first lens 62a and a second lens 62b. The first lens 62a arranged in a line in the light path, the path through which light reflected from the composite diffraction grating 2 of the first-order diffracted light L ₁ incident on the first reflector 12. Further, the second lens system 62b disposed in a light path through which the light path 12 reflected by the first reflector of the first-order diffracted light L ₁ incident on the composite diffraction grating 2.

Further, the length of the optical path from the first lens 62a through the first reflector 12 to the second lens 62b is equal to the sum of the focal length of the first lens 62a and the focal length of the second lens 62b.

The second lens group 63 includes a first lens 63a and a second lens 63b. The first lens 63a is disposed in a light path, and the first-order diffracted light -L ₁ reflected from the composite diffraction grating 2 through the optical path is incident on the second reflector 13. Further, the second lens system 63b disposed in a light path through which the light path 13 reflected by the second reflector of the first-order diffracted light is incident on the compound of formula -L ₁ diffraction grating 2.

Further, the length of the optical path from the first lens 63a through the second reflector 13 to the second lens 63b is equal to the sum of the focal length of the first lens 63a and the focal length of the second lens 63b.

Further, the focal length of each of the first lenses 62a, 62b, 63a, 63b constituting the first lens group 62 and the second lens group 63 is equal to the distance between the composite diffraction grating 2 and the lens 11. Therefore, as shown in FIG. 10A, when the composite diffraction grating 2 is inclined, the optical path after passing through the first lens 62a of the first lens group 62 and the composite diffraction grating 2 are not inclined. The light paths after the lens 62a are parallel. Here, when the first reflector 12 and the second reflector 13 each include two mirrors, when incident on the composite diffraction grating 2 again, the light can be irradiated close to the irradiation point P. With this configuration, the measurement error due to the tilt of the composite diffraction grating 2 can be reduced.

Further, when the first reflector 12 and the second reflector 13 each include three mirrors, when incident on the composite diffraction grating 2 again, the light can be irradiated close to the irradiation point P, and the incident angle and the inclination are incident. The same direction. Therefore, the diffracted light caused by the second diffraction can be stabilized.

As a result, the second incident point formed by the light incident on the composite diffraction grating 2 cannot be deviated from the arbitrary irradiation point P. Further, even when the composite diffraction grating 2 is inclined or the surface of the composite diffraction grating 2 is formed with a wave or the like thereon, the first-order diffracted light L ₁ originally formed on the composite diffraction grating 2 is incident. -L ₁ can also be incident on the irradiation point P, and thus the detection accuracy can be prevented from deteriorating.

Further, when there is a so-called "variation in the third direction Z" such as a tilt (variation) and a gap variation, the wave aberration becomes large, and thus a stable interference signal can be obtained.

Incidentally, similar to the first grating interferometer 64, the second grating interferometer 65 has a first lens 62B and a second lens 63B. Since the first lens group 62B and the second lens group 63B have the same structure as the first lens group 62 and the second lens group 63 of the first grating interferometer 64, the description thereof will be omitted.

Since the other configuration of the displacement detecting device 61 is the same as that of the displacement detecting device 31 of the second embodiment, the description thereof is omitted here. The same advantages as the displacement detecting device 31 of the second embodiment can be achieved by the displacement detecting device 61 having the above configuration.

<4. Fourth Embodiment>

Next, a displacement detecting device 71 according to a fourth embodiment of the present invention will be described with reference to Fig. 11.

Figure 11 is a side view showing the optical system of the displacement detecting device 71 according to the fourth embodiment of the present invention.

The displacement detecting device 71 according to the fourth embodiment is different from the displacement detecting device 31 of the second embodiment in that the light emitted from the light source 3 is linearly polarized and the third phase plate 41 of the displacement detecting device 31 is eliminated. Therefore, in the displacement detecting device 71 of the fourth embodiment, the similar elements are denoted by the same reference numerals as those of the displacement detecting device 31 of the second embodiment, and the explanation thereof is omitted.

The linearly polarized light L is emitted from the light source 3 of the displacement detecting device 71 of the fourth embodiment shown in Fig. 11. Each of the first phase plate 39 and the second phase plate 40 is, for example, a one-fourth wave plate. Further, the first phase plate 39 and the second phase plate 40 convert the second-order diffracted lights L ₂ and -L ₂ belonging to the linearly polarized light into circularly polarized lights having opposite rotation directions. Therefore, the crystal axes of the first phase plate 39 and the second phase plate 40 are perpendicular to each other.

The second-order diffracted light L ₂ , -L ₂ of the circularly polarized light whose two rotational directions are opposite to each other is superposed on each other by the spectroscope 17. Further, the circularly polarized lights whose two rotation directions are opposite to each other are located in the same light path, and are equal to each other so as to become linearly polarized light which is rotated in the polarization direction, and the linear polarization is incident on the first polarization beam splitter 42 or the second polarization beam splitter 46 on.

Since the other configuration of the configuration of the displacement detecting device 71 is the same as that of the displacement detecting device 31 of the second embodiment, the description thereof is omitted here. The same advantages as the displacement detecting device 31 of the second embodiment can be achieved by the displacement detecting device 71 having the above configuration.

Incidentally, in the displacement detecting device 71 of the fourth embodiment, the third phase plate 41 of the displacement detecting device 31 is canceled, and thus the number of components can be reduced.

<5. Fifth Embodiment>

Next, a displacement detecting device 81 according to a fourth embodiment of the present invention will be described with reference to Fig. 12.

Fig. 12 is a side view showing the optical system of the displacement detecting device 81 according to the fifth embodiment of the present invention.

The displacement detecting device 81 according to the fifth embodiment is the same as the displacement detecting device 1 of the first embodiment except that the displacement detecting device 81 is further provided with a second light source 83. Therefore, in the displacement detecting device 81, similar elements are denoted by the same reference numerals as those of the displacement detecting device 1 of the first embodiment, and the explanation thereof will be omitted. Therefore, attention will be paid to the second light source 83.

As shown in Fig. 12, the displacement detecting device 81 includes a first grating interferometer 84 and a second grating interferometer 85. The first grating interferometer 84 and the second grating interferometer 85 have a first light source 3, a second light source 83, and a second beam splitter 88. The second spectroscope 88 superimposes the light emitted from the first light source 3 and the light emitted from the second light source 83 so that the superposed light is irradiated onto one of the irradiation spots P of the composite diffraction grating 2 .

Since the other configuration of the configuration of the displacement detecting device 81 is the same as that of the displacement detecting device 1 of the first embodiment, the description thereof is omitted here. The same advantages as the displacement detecting device 1 of the first embodiment can be achieved by the displacement detecting device 81 having the above configuration.

Incidentally, in the displacement detecting device 81 of the fifth embodiment, when the wavelength of the first light source 3 and the wavelength of the second light source 83 are substantially equal to each other, the first light source 3 and the second light source 83 alternately emit light. And thus extend the service life of the two light sources. Further, even when the first light source 3 is ineffective or troublesome, the second light source 83 can function as a standby light source, and thus the displacement detecting means can be used for a long period of time.

Further, the light emitted from the first light source 3 and the light emitted from the second light source 83 may be linearly polarized light whose polarization axes are perpendicular to each other. In this case, the second beam splitter 88 is a polarization beam splitter. With this configuration, when the first light source cannot be used due to the expiration of the service life or the like, the light source can be switched to the second light source 83, and thus the operation period can be extended. Also, the light loss caused by the spectroscope 17 can be reduced to a minimum.

Further, when the wavelength of the light emitted from the first light source 3 and the wavelength of the light emitted from the second light source 83 are set to different values, the second spectroscope 88 is a wavelength selective filter. In this arrangement, the first grating interferometer 84 and the second grating interferometer 85 can obtain an interference signal by using different light sources under the same conditions of arbitrary irradiation. As a result, high-order diffracted light and stray light can be prevented from affecting each other on the grating interferometer.

<6. Sixth Embodiment>

Next, a displacement detecting device 91 according to a fourth embodiment of the present invention will be described with reference to Fig. 13.

Figure 13 is a side view showing the optical system of the displacement detecting device 91 according to the sixth embodiment of the present invention.

The displacement detecting device 91 of the sixth embodiment differs from the displacement detecting device 1 of the first embodiment in that the reflective composite diffraction grating is changed to a transmissive composite diffraction grating. Therefore, in the displacement detecting device 91, similar elements are denoted by the same reference numerals as those of the displacement detecting device 1 of the first embodiment, and the explanation thereof will be omitted. Therefore, the following description will focus on the composite diffraction grating and the reflector.

As shown in Fig. 13, the composite diffraction grating 92 of the displacement detecting device 91 according to the sixth embodiment is a transmissive diffraction grating. Since the other form of the composite diffraction grating 92 of the displacement detecting device 91 is the same as that of the composite diffraction grating 2 of the displacement detecting device 1 of the first embodiment, the description thereof will be omitted. The diffraction angle of the transparent composite diffraction grating 92 can also be expressed in the same manner as the representation (1) of the diffraction angle of the reflective composite diffraction grating 2.

As shown in Fig. 13, since the first grating interferometer 94 and the second grating interferometer 95 have the same configuration, the description will focus on the first grating interferometer 94. Further, among the elements of the second grating interferometer 95, the elements of the first grating interferometer 94 will be indicated by the symbol "B" to the first grating interferometer 94.

The first grating interferometer 94 includes the light source 3, the lens 11, the first reflector 102, the second reflector 103, the first mirror 14, the second mirror 16, the spectroscope 17, the first light receiving unit 18, and the second light receiving unit. 19.

The first reflector 102 and the second reflector 103 are disposed on the side opposite to the light source 3 and the direction Z, and the composite diffraction grating 92 is interposed therebetween. The first-order diffracted light L ₁ transmitted through the composite diffraction grating 92 and reflected by the composite diffraction grating 92 is incident on the first reflector 102, and the first-order diffracted light -L ₁ is incident on the second reflector 103 on.

Moreover, the first reflector 102 and second reflector 103 of the two first-order diffracted light L _1, -L ₁ different from the two first-order diffracted light L _1, -L ₁ through the diffraction grating 92 Compound The angle (i.e., the diffraction angle) is again incident on the composite diffraction grating 92.

Therefore, the second-order diffracted light L ₂ , -L ₂ which has been transmitted through the composite diffraction grating 92 and is again diffracted by the composite diffraction grating 92 is different from the optical path through which the light L emitted from the light source 3 passes. The light path is incident on the first mirror 14 or the second mirror 16.

Since the other configuration of the displacement detecting device 91 is the same as that of the displacement detecting device 1 of the first embodiment, the description thereof is omitted here. The same advantages as the displacement detecting device 1 of the first embodiment can be achieved by the displacement detecting device 91 having the above configuration.

<7. Variation of diffraction grating>

Next, a variation of the composite diffraction grating will be described below with reference to Figs. 14 and 15.

Fig. 14 is a view showing a first modification of the composite diffraction grating; Fig. 15 is a view showing a second modification of the composite diffraction grating.

The composite diffraction grating 112 shown in Fig. 14 has a radially extending slit s and a slit s which is coaxially arranged and has a substantially circular shape is formed therein. As a so-called rotary encoder, the composite diffraction grating 112 can perform position detection on a rotating portion of a machine tool or the like. Further, with the composite diffraction grating 112, the eccentric component of the second grating vector direction D can be measured when the angle information is detected.

In the composite diffraction grating 2 of the above-described embodiment, the first grating vector direction C and the second grating vector direction D are measurement directions, but the present invention is not limited thereto. For example, the present invention also includes a configuration in which the first grating vector direction C and the second grating vector direction D are not measurement directions, as in the case of the composite diffraction grating 122 according to the second variation of the fifteenth diagram.

As shown in Fig. 15, the composite diffraction grating 122 includes a first diffraction grating 122a and a second diffraction grating 122b. The grating pitch Λa of the first diffraction grating 122a is set to d ₁ , and the grating pitch Λb of the second diffraction grating 122 b is set to d ₂ .

Further, the second diffraction grating of the second grating vector direction B of the D line 122 parallel to the surface of the composite diffraction grating 122 and is inclined at an angle θ ₅ of the first diffraction grating 122a of the first grating vector direction C. Further, the composite diffraction grating 122 is disposed such that the second grating vector direction D is inclined with respect to the first measurement direction X by the angle θ ₆ and inclined with respect to the second measurement direction Y by the angle θ ₇ .

Here, in the case where the angle θ ₅ = 90 degrees and θ ₆ = θ ₇ = 45 degrees, the displacement in the first measurement direction X is by the grating pitch Λa or the second diffraction of the first diffraction grating 122a. The grating pitch Λb of the grating 122b is obtained by multiplying √2. Incidentally, the displacement of the second measurement direction Y can also be obtained in the same manner.

Therefore, the first grating vector direction C and the second grating vector direction D are not necessarily the first measurement direction X and the second measurement direction Y. In other words, the two-dimensional displacement can be detected based on information from the grating pitch of the first diffraction grating 122a or the grating pitch of the second diffraction grating 122b.

Generally, the response speed of the displacement detection is limited due to the processing of the photoelectric conversion electrical signal. Thus, when the moving speed is the same, the smaller the distance of the grating pitch of the diffraction grating, the higher the frequency of the electrical signal becomes. To cope with this problem, as in the composite diffraction grating 122 shown in Fig. 15, the grating vector direction is inclined to the measurement direction, so that the frequency can be reduced, especially in the case of high speed.

As a result, when the moving speed in the same measurement direction is the same, compared with the composite diffraction grating in the case where the grating vector direction is the first measurement direction, the composite diffraction grating 122 shown in Fig. 15 can be used. Reduce the frequency of the electrical signal to 1/√2.

For example, in the case of a semiconductor exposure device having a wafer platform and a reticle stage, the reticle stage does not need to be higher resolution than the wafer platform, but the reticle stage is higher than the wafer platform. The speed moves many times faster. It is known to apply the composite diffraction grating 122 shown in Fig. 15 to the effective line of the reticle stage.

It is to be understood that the invention is not limited to the embodiments of the invention described and illustrated in the accompanying drawings. Although the above embodiment is described using an example in which a two-dimensional displacement system is detected by using a composite diffraction grating having a first diffraction grating and a second diffraction grating and two grating interferometers (as a diffraction grating), However, a displacement detecting device with a grating interferometer can also be used to detect one-dimensional displacement. In this case, a diffraction grating having only one grating vector direction is sufficient for use as a diffraction grating.

Further, the light emitted from the light source can also be supplied through the liquid space or the vacuum space instead of the gas space. Further, each of the light receiving elements of the light receiving unit may be disposed at a separated position by using an optical fiber. With this configuration, the distance between the light-receiving element and the communication portion, such as the relative position information output portion, can be reduced, and the response speed can be improved.

1,31,61,71,81,91. . . Displacement detecting device

2,92,112,122. . . Composite diffraction grating

2a, 122a. . . First diffraction grating

2b, 122b. . . Second diffraction grating

3. . . light source

4,34,64,84,94. . . First grating interferometer

5,35,65,85,95. . . Second grating interferometer

6. . . First relative position information output unit

7. . . 2nd relative position information output unit

10A. . . First virtual surface

10B. . . Second virtual surface

11. . . lens

12,102. . . First reflector

13,103. . . Second reflector

14. . . First mirror

16. . . Second mirror

17. . . Splitter

18. . . First light receiving unit

19. . . Second light receiving unit

37, 62a, 63a. . . First lens

38, 62b, 63b. . . Second lens

39. . . First phase plate

40. . . Second phase plate

41. . . Third phase plate

42. . . First polarizing beam splitter

43. . . First light receiving element

44. . . Second light receiving element

46. . . Second polarizing beam splitter

47. . . Third light receiving element

48. . . Fourth light receiving element

49. . . Third lens

50. . . 4th lens

51a. . . First differential amplifier

51b. . . Second differential amplifier

52a. . . 1A A/D converter

52b. . . 2A A/D converter

53. . . Waveform correction processing unit

54. . . Incremental signal generator

62,62B. . . First lens group

63, 63B. . . Second lens group

83. . . Second light source

88. . . 2nd beam splitter

X. . . First measurement direction

Y. . . Second measurement direction

Z. . . Third direction

P. . . Irradiation point

L ₁ , -L ₁ . . . First order diffracted light

L ₂ , -L ₂ . . . Second order diffracted light

L _d . . . Interference light

C. . . First raster vector direction

s. . . Slit

P. . . Irradiation point

1 is a perspective view schematically showing an optical system of a displacement detecting device according to a first embodiment of the present invention;

2 is a side view schematically showing an optical system of a displacement detecting device according to a first embodiment of the present invention;

Figure 3 is a view showing a composite diffraction grating of one of the displacement detecting devices according to the first embodiment of the present invention;

4 is a view for explaining a positional relationship between a first grating vector direction and a second grating vector direction of a diffraction grating of the displacement detecting device according to the first embodiment of the present invention, and a first grating interferometer and a first 2 map of the positional relationship between the grating interferometers;

Figure 5 is an enlarged view showing a main part of one of the displacement detecting devices of the first embodiment of the present invention;

Figure 6 is an enlarged view showing an amendment of a main portion of the displacement detecting device of the first embodiment of the present invention as seen from the upper side of the composite diffraction grating;

Figure 7 is a side view schematically showing an optical system of a displacement detecting device according to a second embodiment of the present invention;

Figure 8 is a block diagram showing a relative position information output portion of the displacement detecting device according to the second embodiment of the present invention;

Figure 9 is a side view schematically showing an optical system of a displacement detecting device according to a third embodiment of the present invention;

10A and 10B are each an enlarged view showing a main part of one of the displacement detecting devices of the third embodiment of the present invention;

Figure 11 is a side view schematically showing an optical system of a displacement detecting device according to a fourth embodiment of the present invention;

Figure 12 is a side view schematically showing an optical system of a displacement detecting device according to a fifth embodiment of the present invention;

Figure 13 is a side view schematically showing an optical system of a displacement detecting device according to a sixth embodiment of the present invention;

Figure 14 is a view showing a first variation of the diffraction grating;

Fig. 15 is a view showing a second variation of the diffraction grating.

1. . . Displacement detecting device

2. . . Composite diffraction grating

3. . . light source

4. . . First grating interferometer

5. . . Second grating interferometer

6. . . First relative position information output unit

7. . . 2nd relative position information output unit

11. . . lens

12,12B. . . First reflector

13,13B. . . Second reflector

14,14B. . . First mirror

16,16B. . . Second mirror

17,17B. . . Splitter

18,18B. . . First light receiving unit

19,19B. . . Second light receiving unit

L ₁ , -L ₁ . . . First order diffracted light

L ₂ , -L ₂ . . . Second order diffracted light

L _d . . . Interference light

P. . . Irradiation point

Z. . . Third direction

D. . . 2nd raster vector direction

L. . . Light

Claims (3)

A displacement detecting device comprising: a substantially plate-shaped diffraction grating suitable for diffracting light; and a grating interferometer adapted to illuminate light on the diffraction grating, wherein the illumination light is diffracted into two beams, The two beams of the diffracted light interfere with each other and generate an interference signal; and a relative position information output portion is adapted to detect relative position information of the diffraction grating according to the interference signal generated by the grating interferometer, wherein The grating interferometer comprises: a light source adapted to illuminate the diffraction grating on the diffraction grating, perpendicular to the diffraction grating; and two reflectors adapted to reflect two one-time windings that are once diffracted by the diffraction grating Shooting light, and causing the reflected primary light to be incident on the diffraction grating at substantially the same position as the light from the light source; each mirror includes a first mirror and a second mirror, The first mirror reflects the primary diffracted light that is once diffracted by the diffraction grating in a direction different from the incident direction of the primary diffracted light, and the second mirror system refractions that are reflected by the first mirror Shooting light toward the The grating is reflected such that the primary diffracted light is again incident on the diffraction grating at a position substantially the same as the point of illumination from the light source; and the 1 mirror and the second mirror are configured by the The primary diffracted light reflected by the second mirror toward the diffraction grating is different from the incident angle of the light incident from the light source to the diffraction grating and different from the primary diffraction by the diffraction grating. The light is transmitted Passing through the diffraction grating or being reflected away from the diffraction grating at an angle toward the first mirror, incident on the diffraction grating, thereby being reflected by the second mirror and traveling toward the diffraction grating The light path through which the primary diffracted light passes is different from the light path that is diffracted once by the diffraction grating and reflected away from the diffraction grating toward the primary diffracted light of the first mirror, and is different from the light source a light path through which incident light incident to the diffraction grating passes; a beam splitter adapted to overlap two secondary diffracted lights diffracted twice by the diffraction grating; and a receiver adapted to receive The beamsplitters re-circulate the light twice to each other to generate the interference signal. A displacement detecting device according to claim 1, wherein a lens is disposed between the diffraction grating and each of the reflectors. The displacement detecting device of claim 1 or 2, wherein the diffraction grating is a composite diffraction grating having: a first diffraction grating; and a second diffraction grating, wherein the a diffraction grating is disposed along a first grating vector direction parallel to a surface illuminated by the light, and the second diffraction grating is disposed along a second grating vector direction parallel to the surface and opposite to the first 1 wherein the grating vector direction is inclined at a predetermined angle, and wherein the grating interferometer comprises: a first grating interferometer adapted to generate an interference signal of light diffracted by the first diffraction grating; and a second grating An interferometer adapted to generate an interference signal of light diffracted by the second diffraction grating, Wherein the first grating interferometer and the second grating interferometer are arranged such that one of them rotates in a third direction relative to the other such that they form a predetermined angle with each other, wherein the third direction passes through The point at which the light of the source is illuminated and perpendicular to the direction of the surface.